What is a schematic feature class?
A schematic feature class allows implementing a particular type of schematic feature expected in diagrams implemented by a particular schematic diagram template. It is a collection of schematic features that share the same object type (nodes, links, and so on), the same geometry type (point, line, or polygon), and the same schematic attributes for a common area.
A schematic feature class can be associated with one or several schematic diagram templates that implement schematic diagrams containing the schematic features implemented by this schematic feature class. It is assigned to one schematic dataset, although more than one schematic feature class can be defined for the same schematic dataset. Schematic feature classes always exist as physical feature classes in the schematic dataset and contain the schematic features they implement.
Schematic feature classes support parent-child relationships, allowing a child schematic feature class to inherit the parameters of its parent.
The Schematic Dataset Editor is the utility to use to create and define schematic feature classes. Schematics Components (esriSchematic.olb) can also be used to develop schematic feature class creations and define their parameters.
When creating a new schematic feature class, you must specify several properties that will define its structure such as its types, geometry type, spatial reference, attributes, and fields.
Type of schematic feature classes
Four types of schematic feature classes can be specified: Node, Link, Node On Link, and Sub Link.
- The Node type is commonly used to represent a device or other point feature in a schematic diagram. It is the equivalent of a feature junction in a geometric network. Nodes can have geographic, semigeographic, or graphic coordinates.
- The Link type is commonly specified to represent an edge in a schematic diagram. It is the equivalent of a feature edge in a geometric network. A link can be composed of any number of link points, called vertices, that define its path. A link is represented either by a direct single line segment or by several line segments passing through one or more vertices. Each link schematic feature generally corresponds to one feature line or one edge in a geometric network. There is an exception when working with complex edges; in this case, a schematic link corresponds to one network segment that composes complex edges.
- The Node On Link type is used to represent a specific node schematic feature that is always related to a link-type schematic feature where it is positioned. A node on link completely depends on the link it is related to. Moving its related link causes the node on link to move; removing its related link causes the node on link to be deleted.
- The Sub Link type is used to represent a specific link schematic feature that is always related to a link-type schematic feature. A sublink completely depends on the link it is related to. Moving its related link causes the sublink to move; removing the related link causes the sublink's deletion.
Three geometry types are available to represent schematic features. This geometry type and the type of the schematic feature class are linked:
- The Point geometry is generally used for a schematic feature class used to implement nodes or nodes on a link.
- The Polyline geometry is generally used for a schematic feature class used to represent links or sublinks.
- The Polygon geometry may also be used for a schematic feature class used to implement nodes, especially when these schematic features have to behave as containers.
Schematic feature classes also have a spatial reference that defines the coordinate system x,y domain for the schematic features. It is strongly recommended that you specify a spatial reference for each schematic feature class so Schematics can store the geometry of the schematic features in a defined coordinate system.
Unlike the standard feature classes that need to have the same spatial reference when they are regrouped in a feature dataset, the schematic feature classes that reside in a schematic dataset can have different spatial references. It's the same for schematic feature classes that are associated with a particular schematic diagram template; they may also have different spatial references and so have a spatial reference different from the one specified for the schematic diagram template itself.
Schematic attributes and fields
Schematic feature classes also have common attributes and fields. Some of these attributes are physically stored in the schematic feature class as fields, while some others are in memory only; some are linked to the type of the schematic feature class. For example, there are very specific attributes for a node schematic feature class and other specific attributes for a link schematic feature class; some attributes are completely managed by Schematics, while some others can be pure applicative attributes.